Cassini Update

The most recent spacecraft telemetry was acquired on Tuesday, July 24, from the Goldstone tracking complex. The Cassini spacecraft is in an excellent state of health and all subsystems are operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the “Present Position” web page located at http://saturn.jpl.nasa.gov/operations/present-position.cfm.

Wednesday, July 18 (DOY 199):

An engineering activities review was held today for the S37 background sequence. At this review, Spacecraft Office personnel reviewed the activities to be performed during that sequence.

The Titan T34 Radio Science (RSS) bistatic scattering observation, the last in the prime mission, just completed. This observation bounced a radio signal off the surface of Titan – just to the west of the Huygens probe landing site – so that it could be received on Earth. This type of science assists in determining the physical properties of Titan’s surface, including reflectivity, dielectric constant, and roughness. RSS reports that an intermittent surface echo was detectable in the real-time spectra of the X-band data. It appeared in either the RCP or LCP X-band spectra, but sometimes simultaneously in both. It’s a complete data set in the sense that at least one dual-polarization RCP & LCP measurement has been acquired at all three frequencies, as initially planned, and more than one set in the case of X-band.

Thursday, July 19 (DOY 200):

On DOY 200, the Cassini spacecraft flew by Titan at a speed of 6.2 km/sec, and an altitude of 1332 kilometers.

Titan 34 (T34) was unique in that it provided the only opportunity for the Imaging Science Subsystem (ISS) to observe the equatorial or central part of Titan’s dark region at high resolution, better than 50 meters per pixel.
Moreover, the phase angle was low, ranging from 13 to 40 degrees, which is expected to be best for imaging the surface.

During T34, the Composite Infrared Spectrometer (CIRS) made a pair of far-infrared composition studies in both northern and southern hemispheres, 50N and 35S, continuing to search for the beginning of seasonal changes on Titan as northern spring draws near. This pairing was complemented by a complete North-South map of the inbound hemisphere centered on 130W and several more distant observations.

Also during T34, all of the Magnetospheric and Plasma Science (MAPS) instruments observed Titan’s upstream ionosphere. Large scale and distant aspects of Titan’s interaction on the dusk side were also investigated between 10 and 25 Saturn radii. For more details and images link to:http://saturn.jpl.nasa.gov/news/events/titan20070719/index.cfm

Saturn Turns 60 – As was promised last week, here is a detailed report of the discovery of a 60th satellite orbiting Saturn. The newly discovered moon first appeared as a very faint dot in a series of images Cassini took of the Saturnian ring system on May 30 of this year. From then till now, scientists combed the library of Cassini data looking for clues and corroborating evidence. For full details link to:http://saturn.jpl.nasa.gov/news/features/feature20070719.cfm

Friday, July 20 (DOY 201):

On DOY 201, the Radio and Plasma Wave Science instrument (RPWS) performed a lightning whistler observation for around four hours. The reaction wheels were turned off with a transition to thruster control to eliminate any interference caused by the wheels. The spacecraft was in a quiescent state as it pointed at Earth. RPWS then ramped up their data-sampling rate and began listening for possible lightning storms on Saturn.

The main engine cover was re-opened today prior to the scheduled Orbit Trim Maneuver (OTM) #122. This completes the 34th close/open cycle since launch.
The next closure is scheduled for August 29, 2007, in S33.

Scheduled to execute on Saturday, July 21, the Titan 34 cleanup maneuver,
OTM-122, has been cancelled. A reaction wheel bias to replace the one
coded into the maneuver will be approved today along with commands for a bias previously scheduled for the pass on Sunday. Both will be uplinked on Saturday. The next OTM, #123, is scheduled for Aug. 5.

Today there were non targeted flybys of the satellites Helene and Tethys.

Monday, July 23 (DOY 204):

A change control board meeting was held today for Attitude and Articulation Control Subsystem (AACS) Flight Software (FSW) Version A8.7.6. This FSW version will update the secondary safing vector pairs, and the default thruster force magnitudes. The software will be uplinked to the spacecraft in early January, 2008, after the Titan 40 flyby, and will cover the time frame from January 10, 2008 to June 15, 2009.

Tuesday, July 24 (DOY 205):

Opportunities for some classic images presented themselves this week. On DOY 203 an image was taken of the combination of Mimas, the rings, and Saturn. On DOY 205 the image was of Tethys, Hyperion, and Enceladus.

A one-hour documentary on Saturn, which is part of the History Channel’s “The Universe” series, is airing tonight at 9 p.m. Eastern. Several Cassini scientists will be featured.

Two topics were discussed at the Mission Planning Forum. One was a report on the progress made since the release two weeks ago of the proposed Extended Mission DSN Strawman plan. Addressed were the latest changes that have been incorporated, and what tasks remain before the start of integration.

The second topic dealt with how Cassini would respond, and what S32 contingencies should be in place, should the Phoenix launch be unable to go as planned on August 2-3. A reschedule would potentially impact the DSN station allocation for Cassini and thus science data playback. Discussion covered what passes might need to be downgraded if the Phoenix launch is
rescheduled, and what the impact would be to Cassini. If the flight team
lays plans for how to respond now, it will make implementation much easier if it becomes necessary. Of course, the team is hoping that it will all be unnecessary. The Project sends its best wishes to Phoenix.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington, D.C. JPL designed, developed and assembled the Cassini orbiter.